Hydraulic transmission system



Dec. 13, 1938.

O LJUNGSTROM HYDRAULIC TRANSMISSION SYSTEM Filed Aug. 14, 1935 8 Sheets-Sheet l INVENTOR O.L/ungs/'rom BY @MVX JW ATTORNEY Dec. 13, 1938. o. LJUNGSTROM 2,139,965

HYDRAULIC TRANSMISS ION SYSTEM Filed Aug. 14, 1935 8 Sheets--Sheerl 2 68 Q 4o 4| ATTORNEY Dec. 13, 1938.' o. LJuNGsTRoM HYDRAULIC TRANSMISSION SYSTEM Filed Aug. 14, 1935 8 Sheets-Sheet O. jungs/'fom ATTORNEY Dec. 13, 1938. o. LJUNGSTROM HYDRAULIC TRANSMISSION SYSTEM Filed Aug. 14, 1935 8 Sheets-Sheet 4 INVENTOR Dec. 13, 1938.

O. LJUNGSTROM HYDRAULIC TRANSMISSION SYSTEM Filed Aug. 14, 1935 Sheets-Sheet 5 www af, www

ATTORNEY Dec. 13, 1938. *I o. I JUNGSTROM v 2,139,965

HYDRAULIC TRANSMISSION SYSTEM Filed Aug. 14, 1935 8 Sheets-Sheet 6 4seo BUGS/W" pressure /wulucnd by com spgen/ a; sm. M aan.

INVENTORl O. jungs/rom BY mw mf ATTORNEY .D80 13, l.938- o. LJUNGsTRoM 2,139,965

HYDRAULIC TRANSMSSION SYSTEM I Filed Aug. 14, 1935 8 Sheets-Sheet T Z113. ZZ

DIREOTION or now OF POWER WHEN REDUCER ROTATES OPPOSED To DIRECT ION OF BOOSTER PRESSURE PRODUCED BY REDU CER POWER INUT TO HYDROGEHR POWER OUTPUT 'FROM HYDROGE'R ZQQ- .72.

DlREcTION or `FLOW O? POWER WHEN REDUCER RO TATES MTH DmEcTION OFBOOSIER PRESSURE PRODUCED BY BOOSTER POWER INPUT To POWER OUTPUT 'FROM HYDROGEAR HYDROGEAR N 2 I mmm o -L O; Y n

UUU 89 29 6.9 l W o 78 gmc/VWM Ojj'anysf/om ma, 4 @M di. MM

Dec. 13, 1938. v o. LJuNGsTRoM 2,139,965

HYDRAULIC TRANSMISSION SYSTEM Filed Aug. 14, 1935 8 Sheets-Sheet 8 NEUTRAL Eng/'nz and soesler rafale a fd/lng speed,

Reducer rola/ing efnpaagd la Boas/er, o pressure furnished.

Driven sha/f und Pla/ef cage s/afonsry. Regula/fm; ,w'sfon esl/'ng on Reverse pis/en slop.

STAT/@MARY neat/:ER

wg/'ha und Boost@ ohr/e.

al modera/n speed. Ree/ucar .lM/fobqryl no pressura /u/nlS/:QQC af/'ven :ball and Plane/- cage fafa/e will) direc/fno o Booster.

Regola/ing pis/'on has /e/ Reverse p/.son s/ep.

DIRECT DRIVE eng/e und soos/ef, educa und on'ven sho/f ro/oe w//A same speed und 1' sama oir-ech'gn.

Pressure produced by MIX/MUM FORWARD MAX/M UM REVERSE E09/ne and sans/hr fahr/c al increased speed. vedocc be.. incrgased rola/fol) wasma'lboaslef; fessura ,cfeu's'uced Ay Rede/cgi: Driven waff ad P/ene/ cage ro/be o/Fosedfq Boas/zin #eve/'se )wis/ob avvenisse/'nsf 175 spr/'09, @lsu/afar pis/an flo/lla ws.

VINVENTOR `O. jungs/rom ATTORNEY Patented ec. i3, i938 was 2,139,965 e mancare fraansssion srsrEM 010 Liungstrom, Detroit, Mich.,` assigner, by. mesne assients, to The Bower Transmission Company, Incorporated, a corporation rof Delaware Application aut i4, i935, serial No. 36,206

3d ma This invention relates to transmission systems and in particular to variable speed transmission systems in which the speed of the driven shaft may be varied smoothly and progressively from 5 zero to a maximum in either direction without the neceessity of shifting gears. My invention is particularly suitable for use in driving vehicles from internal combustion engines, although it is not limited to such use, and may be used wherever it is necessary to start and accelerate heavy loads.

An object of my invention is to devise a transmission system in which the transmission ratio is automatically varied in accordance with the speed of the driving shaft.

A further object of my invention is to devise a transmission system in which the transmission ratio is dependent upon the torque being transmitted.

20 Another object of my invention is to devise a transmission system in which the transmission ratio is dependent both upon the speed of the driving shaft and upon the torque being transmitted.

vise a transmission system in which no power will be transmitted from the driving shaft to the driven shaft so long as the speed of the driving shaft is below a definite value, and driving power is automatically applied upon the speeding up of the driving shaft.

When my transmission system is employed in an automobile, the usual clutch construction and. its control pedal is eliminated, the usual gear shift lever is mit needed, and the, entire operation of the car is controlled simply by the operation of the engine throttle.

My invention also involves a novel speed-responsive servo-motor, and a novel arrangement for lubricating dilerential gearing.

In the preferred embodiment of my invention the major portion of the driving power is transmitted,mechanically from the driving shaft to the driven shaft through gearing having fixed meshing relations, and the minor portion of the power is transmitted through a variable ratio hydraulic transmission link. The mechanical transmission elements consist of Ya differential gearing, the internal gear of which is driven by the driving shaft andthe planet spider is connected with the driven shaft. 4The hydraulic link .consists of a convertible pump (hereafter termed a booster) driven from 4the driving shaft and hydraulically connected with a second reversible -pump (hereafter termed a reducer) Still another object of my-invention is to de-` (Cll. 6Q-53) mechanically connected with-the pinion gear or heating element of the jdiiferential gear.l Onev of the pumps, preferably the booster, is provided with means to varyits displacement, lWhile lthe other pump has a xed displacement.` vThe two pumps are connected in a 4fluidcircuit so that vwhile one pump is acting as a fluid pump the other unit is acting as a fluid motor andvice versa. The working medium, or uid may be either a liquid or a gas, but `I prefer a liquid.

The preferred embodiment of my invention is described herein with particular' reference toits use as a transmission system for automobiles. In this particular use,.the arrangement is such that with the car standing still and the engine .operating at idling speed, both the reducer and the booster operate as pumps for circulating fluid l in the same direction in the .hydraulic circuit.

The displacement varying mechanism forthe booster is normally biased to a position solthat the output of the booster'will be equal to the output of the reducer, and there will be no reaction upon the rotors of these two units except that necessary to overcome the friction in the fluid circuit. Under these conditions, the reducer rotor rotates freely in a direction opposite to engine shaft rotation, and no power is transmitted from the engine to the propeller shaft. The displacement varying mechanism of the booster is automatically controlled byA an arrangement which is responsive to the speed ofv the engine shaft, and the arrangement is such that as the engine shaft increases above idling speed, the displacement of the booster is gradually reduced to zero and then gradually increased in the opposite direction, in other words, the displacement ofthe booster is changed so as to reverse the ow of uid in the fluid circuit.

As the engine speed is increased above idling speed, the displacement of the booster is firstreduced, thereby decreasing the capacity` ofthe booster below that of the reducer and causing a reaction upon the reducer rotor which in turn causes the application of driving torque to the propeller shaft. yDuring this stage the reducer is acting as a pump, supplying fluid to the boost, er, and the booster is acting as amotor adding its torque to the engine torque. As the displacement ofthe booster is further reduced, the speed of the reducer rotor is further decreased, thereby causing the propeller shaft to increase in speed. When the displacement of the booster is reduced to zero, the :duid circuit is blocked and the rotor of the reducer is'held stationary,l and under this condition the drive ratio is determined by the ratio of the pitch diameters of the internal gear and the pinion gear in the differential gearing.

Upon further increase in engine speed,` the y displacement of the booster pump begins to increase in the opposite direction from the initial displacement, and the boosterlbegins to act as a pump circulating fluid in the opposite direction in the circuit. The reducer rotor now reverses its direction of rotation and begins to operate as a motor. As soon as the speed of the reducer rotor attains the speed of the propeller shaft, the transmission ratio is one-to-one, or direct drive is obtained. Upon further' increase in speed of the engine, the displacement of the booster is further increased, thereby driving the reducer rotor at increased speed and causing the propeller shaft to be driven at a speed in excess of the speed of the engine shaft.

By increasing the booster displacement above its normal or biased value and in the same direction, the propeller shaft is driven in a reverse direction.

In addition to the control of the booster displacement in response to the speed of the driving shaft, I' provide means responsive to the pressure in the fluid circuit (which is proportional to the torque being transmitted) for opposing or reducing the action of the speed-responsive means, thus limitingr the amount of pressure (or torque) which is developed at .any given`engine speed.

A preferred embodiment of my invention is illustrated in the accompanying drawings in which:

Figure 1 is a longitudinal section through the transmission; Figure 2 is a sectional View of the transmission along the line 2 2 in Figure 1;

Figure 3 is a sectional view ofthe transmission along the line 3 3 of Figures 1' and 9;

Figure 4 is a sectional View ofthe transmission along the line 4 4 in Figure 1;

Figure 5 is a sectional View of the transmission along the line 5 5 in Figure 1;

Figure 6 is a sectional view along line 6 6 in Figures 3, 5 and 9 illustrating the details of the regulating valves;

Figure 7 is a sectional view taken along line 1 1 in Figures 3 and 9 illustrating the details of the control pumps; Y

Figures 8, 8b, and 8c show four views of a roto vane employed in the pumps;

Figure 9 is a side elevational view of the transmission showing the regulating mechanism in section along line 9 9 in Figures 3, 4 and 5.-

Figure 10 is a graphillustrating the operation of the transmission;

Figures 11 and 12 are diagrammatic representations of the transmission system indicating the direction of power flow;

Figure 13 is a fragmentary view, partly in section, vshowing a modified control arrangement;

Figure 13a is a fragmentary sectional view of the control valve of Figure 13 showing the position of the discharge port and passage;

Figures 14 to 18 are schematic diagrams illustrating the different stages of operationof Athe transmission.

Referring to the drawings:'| is the driving flange of the transmission to be bolted to the shaft of the driving engine (not shown) or other source of power. The sleeve extension la of the flange I has external splines on which the damper sleeve 2 is mounted, free to slide on sleeve Ia so as to prevent any axial strains from being transmitted between the engine and the transmission.

One end of damper sleeve 2 is journaled in end-plate 8a of housing 8, while the other end.

of the sleeve has journaled thereon an end-plate 3a of the rotatable gear housing 3. The sleeve 2 is also provided with a flange 2b located between plates fla and 8G, and this flange is coupled to the plate 3a by resilient coupling devices to prevent vibrations from being transmitted from fiange l to the gear housing 3. These coupling devices may be formed of helical springs 2c mounted between plate 3a and a ring 3b carried by the plate 3a, the springs being 1ocated in recesses or holes formed in flange 2b and ring 3b in such manner that the driving torque is transmitted through the springs from flange 2b to plate 3a. The ring 3b is supported from the plate 3a by a numb-er of pins 2e freely passing through holes formed in the flange 2b. 'Other forms of resilient couplings may be used if desired, and a number of these devices are distributed around the sleeve 2.

The rotatable gear housing 3 encloses a differential gear set, and the internal gear 3c of the set is preferably formed integral with the housing 3.

Gear housing 3 has a sleeve extension 4 to which the booster rotor 5 is keyed. Two needle roller bearings 6 and l are arranged one on each side of the rotor 5 for the purpose of 1ocating the rotor and the gear housing 3 in housing 8. Spiral gear 9, which serves the purpose of driving the gear pumps, is also keyed tothe extension sleeve 4. The internal gear 3c, meshes with three equally spaced planet gears I0 of which only one is shown in the sectional view of Figure 1. The planet gears are mounted on planet pins I! by means of needle rollers I2. Planet pins- I I are located inplanet cage I3 which is secured to and carried by the driven shaft I4. A plain bearing I5 in the drive flange sleeve I a supports on'e end ofshaft I4 and ball bearing I 6 supports the other end of the shaft in the opposite end of the transmission. Mounted on the driven shaft i4 is the tachometer takeoff worm I'l and gear Ila and the power takeoff flange I8. Driven shaft I4 is made hollow for reduction in weight and for the purpose .of carrying lubricant to'the different points to be lubricated. Spring disks I4a and I4b are provided to close the ends of the shaft to prevent escape of the lubricant. The lubricant enters the shaft through holes I9 from an annular groove formed in gland 20. A duct I4c formed in planet cage I3 feeds lubricant from hollow shaft I4 to hollow pins II, which are also provided with spring disks closing the ends. Hollow pins II are provided with radial ducts Ila for supplying lubricant to the needle roller bearings I2. A duct or hole I4d serves to supply lubricant from shaftll4 to the bearing I5 between sleeve Ia and the shaft I4.

The planets mesh with pinion 2| which is formed on-the end of a hollow shaft 2Ia surrounding driven shaft I4. On pinion shaft 2Ia is mounted the reducer rotor 22 supported in needle roller bearings 23 and 24 on opposite sides thereof. A sleeve 25 secured to shaft I4 forms a supporting bearing for the other end of shaft 2 la, and a duct or hole I4e supplies lubricant to this bearing and to gear 2| from shaft I4.

Housing 8 has a flange 26 for boltlng to the frame of the driving engine. This housing surrounds the damper, differential gearing and booster rotor. The rotor 5 rotates inside of a 75 movable liner 21 which is closed in by cover 28 containing bearing 1. An intermediate housing 29 vsurrounds the pump driving gear 9 and reducer rotor 22 which rotates inside of the fixed liner 55. This part of the housing has two passages 30 and 3| forming a uid circuit for they transmission of the hydraulic medium between theV booster and the reducer rotors. On the highest part of the passage 30 is placed a needle valve 32 for relieving the air when the unit is first filled with liquid. Passage 3| has in its lowest point a drain plug 33. A sump 34 for storage of liquid is made -part of thevhousing.

The reducer rotor 22 is closed in by cover 35.

End housing 36 contains bearing I6 and gland 20.

-Figure 2 is a sectional view taken along line 2 2 inFigure 1, showing the differential gear construction including the internal ygear 3c, the three planet gears I0, the planet cage I3 and the pinion gear 2| A Figure 3 is asectional view of Figure 1 along line 3-3, showing intermediate housing 29 containing spiral gears 9 and 31 for driving the gear .control pumps. The pump drive shaft 31a is an extension of gear 31 and is located in ball bearing 38 and plain bearing 39, and to the lower end of the shaft is keyed pump gear 40. The pump housing 4| is bolted to the underside of the sump. The intermediate housing further forms the cylinder 42 for the power piston which operates the movable liner 21 in Figure 1, and

. this cylinder is provided with a liner 43. In the housing is also arranged the nearly constant pressure valve consisting of sleeve 44, piston 45, ad'- justing screw 46,\spring.41 and cap 48. This valve-regulates the pressure of the uid supplied from one of the control pumps to cylinder 42 for operating the power piston. relatively high.

Figure 4 is a sectional View along line 4-4 in Figure 1, and shows the booster rotor 5. and six rotor vanes 49 which are mounted radially and free to slide in radial direction in the rotor. The movable liner 21 can be moved to the right or to the left to form variable eccentricity with the rotor in both directions and is held in' position by a square-thread screw 50. The screw is located in the intermediate housing by ball bearing 5| and is operated by lever 52 which in turn is operated by the power piston by means of connecting rod 82 in Figure 9. Cored opening 53 This pressure is .conveys the lubricant from the differential gear` housing 8 to thesump. Opening or duct 53 also serves to drain fluid from the space between the liner 21 and the casing wall, as shown by the passage connecting the space to the right of liner 21 with the duct 53 in Figure 4.

Figure 5 is a sectional view along line 5-5 in Figure 1, and shows the reducer rotor 22 and six rotor vanes 54 which are also movable radially in the rotor. Surroundng the rotor and vanes is a liner 55 mounted with fixed eccentricity with respect to the rotor. The upper passage 38 and the bottomi of the sump 34 are equipped with cooling fins 93 and 92 to dissipate the heat of friction. The rotor Vanes 49 and v54 are held against the liners 21 and 55 by means of spring rings 56 and 51 shown in Figure 1.

The details of the regulating valves for the control pumps are shown in Figure 6. The valve consisting of sleeve 44, piston 45, adjusting screw 46, spring 41 and cap 48 is arranged to act as an over-o'w or relief valve in the outlet passage 68a leading from the pump 68 which supplied the working fluid to the power piston. When the pressure in passage 68a exceeds a certain limit, piston 45 is moved against spring 41 and.r uncovers discharge apertures 44a formed in sleeve 44 and allows the iiuid to escape into the sump 34. By proper design of the spring 41 and the discharge aperture ofthe valve, the valve opcrates to maintain a substantially constant pressure of relatively high value in the outlet passage 68a regardl :ss of pump speed.

The valve 58-60-62-64-66 is arranged'to form an over-flow valve for the outlet'passage 69a from the control pump 89 which supplies a variable fluid pressure to the control piston of the servo-motor. Movement of piston 60 variably uncovers discharge aperture 58a formed in sleeve 58 according to the pressure in passage 69a, and the uid escapes through the aperture into the suinp 34. By proper design of the spring 64 andtil it is suicient to move the piston 60 and un-v cover enough of the discharge aperture 58a to accommodate the output at that particular speed. As the engine speed increases further, the pressure existing in passage 69a will correspondingly increase and force the valve open to uncover a larger area of the discharge aperture, and thus the pressure developed in the passage 69a becomes a function of the engine speed.v

'Ihe valve 59-6I-63--65--61 is arranged toA act as an over-flow valve for the outlet passage 10a of the pump 10 which supplies lubricant to iill the Huid circuit' 39-3| through the, passage 10a, Figure 5. The valve operates to maintain a substantially constant pressure output -of the pump at -relatively low value. Fluid from passage 1|la passes through discharge aperture 59a formed in sleeve 59 and discharges into sump 34. The aperture here is relatively wide and the spring B5 has a steep characteristic. The pump 10 also supplies lubricant under pressure through a cored Ypassage 36h which connects the low pressure fluid passage 3| with passage 36a which in turn is/ connected tothe gland 29, from which point the lubricant passes into the shaft |4 and then to various parts of vthe transmission as described above. g

The.va1ve consisting of cylinder 1I, piston 12, adjusting screw 13, abutment 14, springJ 15 and cap 16 is arranged to be influenced by the pressure in passage 11 leading from the passage 30 in iiuid circuit, see Figure 5. The aperture i in the piston 12 lis arranged to relieve the pressure in outlet passage 69arof pump S9 which supplies fluid pressure to the control piston of the servomotor,`I andkto thereby change the standardl of operation of the servo-motor. An increase in pressure in chamber 11 causes piston 12 to move against spring 15 and variably uncover aperture i in accordance with the pressure and allows fluid from passage 69a to escape through openings 1|a iny cylinder 1|, through the aperture i -into the hollow piston 12, and back through the -piston and out into the sump 34 through holes 1lb formed in the enlarged head of the piston.

The degree of control over the servo-motor by the valve 1.I12 will depend upon the design of the spring l5 and the size and shape of the aperture i. I prefer to form this aperture with a tapered shape as shown in order to obtain a graduated control with the movement of the piston 12. The arrangement is such that increasa ing pressure in the uid circuit causes a reduction in the pressure in the outlet passage 69a of the pump B9.

Any desired cltiaracteristicI of the regulating valve may be obtained by proper design oi the spring and the valve aperture. VBy using a spring with a at characteristic and a wide aperture, a nearly constant pressure is obtained; whereas a spring oi steep characteristic in combination with a narrow aperture will give a variable presn sure characteristic. The pressure characteristic maybe controlled by proper design of the sides of the aperture, that is, ,by proper design of the shape of the aperture.

Figure 7, a section along line 1 1 in'Figures 3 and 9, shows the arrangement of control pumps 68, 69 and 18 which are driven by common gear 48 at a speed proportional to the engine speed. The suction and pressure sides are indicated on the drawings by S and P respectively. Pump 68 supplies fluid under pressure to the power cylinder 43 through cored passage 68a and annular passage 68h. Pump 59 supplies uid of variable pressure to control cylinder 85a or to cylinder Sla through passage 89a and valve 19. Pump 10 supplies lubricant to section 3l of the fluid circuit through passage 18a and to gland 28 froml section 3i through passages 36h and 36a- All pumps have a common housing 4l which is bolted to the underside of the sump as shown in Figure 3. i

Figures 8, 8a., 8b and 8c show various views of a vane used in each of rotors 5 and 22 and are numbered 49 and 54. The vane is shown in side elevation in Figure 8, in end-view in Figure 8U, in verticallsectional view in Figure 8b, and in bottom view in Figure 80. rIhese vanes are of the same construction but differ in size. The vanes are provided with cavities a and b on opposite sides below the surface of the rotor, and these cavities are connected to the pump spaces on opposite sides of the vane by holes a and b so astovbalance the side pressures in order that the vanes will oat freely in the slots. All other grooves and holes are for the purpose of Weight reduction. I The pressure of the vanes against their respective liners 21 and 55 if they were left heavy would be considerable at high rotor speeds due to centrifugal force.

The construction of the servo-motor for operating or varying the eccentricity or displacement of the booster is shown in sectional view in Figure 9. The power piston 88 is connected to lever 52 by means of link 82. This piston receives working iluid from pump 68 (Figure '1) at a relatively high pressure, which pressure is kept 'nearly constant by valve 45 (Figures 3 and 6) regardless of the speed oi` the pump. The fluid enters cylinder 43 through holes 83 from an .annular passage 6817 surrounding the cylinder and is directed to one i. side or the other of the piston by means of a pilot valve consisting of a movable sleeve 84 arranged in a cylindrical bore in piston and cooperating with valve ports formed integral with piston 88. Annular ports c and f communicate with the annular space on the outside of piston 88 which is supplied with fluid under pressure, from passage 68o. Annular port d communicates with the right end of cylinder 43 through passage. e, and annular port g communicates `with the left end of the cylf inder through passage h. ,Sleeve 84 is provided openings n formed in sleeve 9d. The pilot valve' Se is moved by regulator or control piston which is counterbalanced by the regulator or biasing spring 88, and is operated by means of liquid from pump 69, (Figure 7) supplied to control cylinder 85a. This liquid has a variable pressure, varied with the speed of the driving engine in such a manner that if the engine speedis increased the pressure will rise and move regulator piston 85 to the left against its spring 86 and pilot valve 84 will move into a position to admit fluid under pressure to the right end of cylinder 43 through ports c, 7', d and e and to drain the left end of the cylinder through ports h, y, m and n. The power piston now moves to the left and by means of link 82 and lever 52 will rotate screw 50 (Figure 4),

which in turn will change the eccentricity of the booster by moving liner 21 into a riew position of less capacity. Movement of the power piston closes the passage e and the piston will remain in this position until further movement of part 84. If the sleeve 84 should return to its biased position, iiud pressure will be admitted to the left end of the cylinder through ports f, lc and g and the right end would be drained through ports d and m, thus causing the piston to return to its'original position. The arrangement is Such that the power piston will follow the movements of the control valve sleeve 84. The piston 88 is provided movement being sufficient to open the valve portsg or d.

The control piston 85 is held in its normal or biased position by an adjustable stop screw 81 carried by piston 8| arranged in an auxiliary control cylinder Bla. The auxiliary control cylinder 81a is mounted in axial alignment with cylinder 85a with a common cylinder head 85h interposed between the two, and the stop pin 81 extends through the head 85h into the cylinder 85a. The piston 8| is normally biased to the position shown in Figure 9 by a spring-88 which is stronger than the spring 86. A control valve 19 operated by a lever 18 serves to supply fluid either to the main control cylinder 85av for forward operation or to the auxiliary control cylinder 8Ia for reverse operation. A relief passage 89 arranged parallel with pressure passage 69a (Figures 5, 9 and 13a) is arranged to drain fluid from control cylinders 85a or 8Ia, depending upon the position of valve 19. In Figures 9 and 13 the valve 19 is set to drain the cylinder 8|a and to supply fluid under pressure to cylinder 85a. Figure 13a is a fragmentary section through the head'85a along the axis of passage 89 showing how the valve 19 drains cylinder 8Ia. When the arm 18 is moved to reverse position", the valve 19 will drain cylpiston 85 away from its biased position, and the 75 normal position of the control elements is shown in Figure 9. Under this condition and with the vehicle standing still both the booster and the reducer operate as pumps to circulate fluid in the same direction and with equal capacities (see Figure 14) so that the reducer rotor rotates freely and there is no reaction on the reducer rotor, and hence no torque applied to the propeller shaft.

As the engine speeds up, the power piston moves the displacement lever 52 to the left from the neutral position and gradually decreases the displacement of the booster, thereby decreasing the capacity of the booster below that of the reducer and causing a reaction on the reducer rotor which in turn causes torque to be applied to the propeller shaft and the vehicle begins to accelerate.

During the stage in which the booster displacement is being decreased, the reducer rotoris rotating in a direction opposite to the engine rotation, and all of the power transmitted ows through the differential gear as shown in. Figure When'the displacement of the booster is reduced to zero the fluid circuitis blocked by the booster rotor, and the reducer rotor is held stationary, as shown in Figure 15.

Upon further increase in engine speed as the vehicle accelerates, the booster displacement is reversed, and the booster begins to supply uid in the opposite direction to drive the reducer in the same direction of rotation as the engine, and under this condition, the major portion of the power is transmitted through the differential gearing, and a minor portion transmitted through the hydraulic circuit, as shown in Figure 12. Figure 16 illustrates the reversal in displacement of the booster and the reversal in flow of :Suid in the circuit during this stage. Y

Figure 17 shows the operation of the system where the displacement of the booster has been increased to its maximum value for forward peration, and by proper design, the reducer rotor may be driven at a speed sufficiently high to produce over-speed drive of the propeller shaft.

If the driving shaft is brought downto idling speed, the pump drive will be accordingly reduced in speed, the liquid pressure in the regulator pump valve 58 will be lowered, the regulator piston 85 4will return to the stop screw 8l, and the driven shaft will come to a stop with the driving shaft still rotating.

When it becomes Vnecessary to reverse rotation of the driven shaftlreverse lever 'I8 is moved to a position marked Reverse in Figure 9, thus moving rotary valve 19 to a position permitting the regulating liquid to operate reverse piston 8i against its spring 88 and thereby moving the stop screw away from regulating piston 85 which will now follow the stop screw under the action of the regulator spring 86. The liquid pressure in the control cylinder 85a has been removed by means of a relief passage 89 parallel to pressure passage 59a Figure 5. This relief passage ends in the sump 34 Figure 1. The regulating liquid pressure now acts upon the reverse piston in exactly the same manner as on the piston 85 for forward operation.

It will be noted that the operation of the servomotor is under the joint control of the variable pressure pump 69, responsive to the'engine speed, and under the control of the regulator valve lll2 which is responsive to the pressure in the fluid circuit (or to the torque being transmitted). The pressure required in the fluid Circuit to initiate operation of the valve Tlf-12 inmodifying the trical regulator.

speed responsive control is determined by the tension of the spring l5, and, accordingly, the pressure at which the valve becomes effective may be varied by varying the tension of spring- 15. The arrangement is such that increase in pressure in the iluid circuit tends to reduce the fluid pressure output of the speed responsive pump 69. This control feature is especially useful in allowing the engine to speed up and deliver its maximum horse power when increased torque is applied to the propeller shaft, as in case of driving the vehicle up steep grades. It also prevents the transmission ratio from changing too rapidly during acceleration, and prevents the building up of excessively high pressures in the iiuid circuit. In case the car is accelerated quickly, and high pressures are developed in the circuit, the valve 'll- 12 retards the operation of the servo-motor until the car accelerates and the pressure decreases in the fluid circuit, whereas, if the car is accelerated gradually the operation of the servo-motor is governed principally in accordance with the engine speed.

Curve sheet Figure 10, illustrates the performance of the transmission system where the ratio `of the pitch diameter of theengine gear to the pinion gear is l to 3. On it is indicated a.` neutral line, forward and reverse speeds, reduction and overspeed ranges as well as the direction of rotation of the reducer rotor, and by which rotor the liquid pressure is produced;

By assuming a certain engine speed, which is the speed of the driving shaft, and choosing a V speed of the driven shaft, it is possibleto determine from the diagram the speed of the reducer, the direction of rotation of same and whether reduction or overspeed is obtained.

In case the booster has a fixed displacement and the reducer has a variable displacement, the servo-motor should be arranged to increase the displacement from its normal or biased value for forward operation, but with this arrangement, overspeed drive cannot be obtained. For .reverse operation, the displacement of the reducer would be decreased from its normal value, but it is never reduced to zero. 4

The novel control features disclosed in connection with the hydraulic transmission link are not limited to use in a mixed transmissionl of the type illustrated, but are useful in a straight hydraulic for zero booster displacement, but otherwise the operation would be the same as described above.. I prefer, however, to use the differential gearing in order to reduce the size of the hydraulic units and to obtain awider range 'of speed and torque yvariations. l

The specic construction disclosed herein is for' the purpose of illustration only, and it will be clear to those skilled in the a'rt that many changes may be made ,without departing from the scope of my invention.f For example, other known pump constructions may be used in the fluid circuit having different arrangements for varying and reversing the displacement, and other known forms of speed responsive devices may be used to control the displacement varying means, such as a centrifugal regulator or a speed responsive elecmay be simplified by omitting the power piston and pump 68, making spring 86 strong enough to bias the lever 52 to the neutral position and designing pump 69 to have suflicient power to op- Also, the control arrangement` erate the lever 52 directly and without the aid of the power piston, This simplified arrangement is illustrated in Figure 13 which is a fragmentary sectional view showing the details of the control arrangement, using the same reference characters as Figure 9. In this arrangement, it will be seen that the power cylinder and piston of the servo motor and the pump 68 have been eliminated and the lever 52 is operated directly from the piston 85, but otherwise the construction is substantially like that shown in Figure 9.

It will be understood that the speed responsive control arrangement disclosed herein for varying the displacement of the booster may be used without the pressure responsive control valve 'll- 12, however, I prefer to use the joint control responsive to both speed and pressure.

'Ihe term convertible pump as employed herein denotes a pump which will operate either as a fluid pump or as a fluid motor. The term reversible displacement denotes that the displacement may be changed to reverse the direction of flow of fluid during pump operation without reversing the direction of rotation, or, for motor operation, to reverse the direction of rotation withvention and illustrated a preferred embodiment thereof. Certain modifications have been pointed out-to indicate the broad scope of the invention. Various other modifications will occur to those skilled in the art, andI desire it to be understood that all modifications which fall within the terms of the appended claims are to be considered as falling within the scope of my invention.

I claim:

1. In combination, a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a convertible iluid pump connected with the floating member of said gearing, and means responsive to increasing speed of said power shaft for imposing an increasing load on said pump to decrease its speed and stop the rotation thereof and for thereafter driving said pump as a motor in the opposite direction.

2. In combination, a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a convertible uid pump driven by said power shaft', a convertible fluid pump connected with the floating element of the differential gearing and connected in fluid circuit with the flrst pump, and means responsive to speed variations of said power shaft and operable at low speeds of the power shaft to cause the second mentioned pump to drive the rst mentioned pump as a motor in the direction of power shaft rotation and operable at higher speeds of said shaft to cause the first pump to drive the second pump as a motor.

3. In combination, a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a fluid pump driven by said power shaft, a fluid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, one of said pumps having means'for varying the displacement thereof, means for normally biasing said 'displacement varying means to a position to cause necting said shafts. a convertible fluid pump a variable speed power 'driven by said power shaft, a convertible fluid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, said rst pump having means for varying and reversing the displacement thereof', means for normally biasing said displacement varying means to a position to cause the firsty pump to circulate fluid in the same direction in said circuit and at the same capacity as the second pump when the driven shaft isstationary, and means responsive to increase in speed of the power shaft to flrst decrease the displacement and then reverse the same and increase it in the opposite direction.

5. In combination, a variable speed power shaft, a load shaft, a fluid pump driven by said power shaft, means for varying the displacement of said fluid pump, a fluid motor mechanically connected with the load shaft and connected in fluid circuit with said pump, means for normally biasing the displacement element of said pump to a position to prevent the transmission of power between said pump and motor, and means responsive to increase in speed of the power shaft for varying the displacement of said pump to transmit power from the pump to the motor.

6. In combination, a variable speed power` shaft, a load shaft, means for transmitting power from the powerv shaft to the load shaft comprising a fluid pump driven by the power shaft and connected in fluid circuit Iwith a fluid pump connected with the load shaft, one of said pumps being provided with means for varying the displacement thereof, means for normally biasing said variable displacement element to a position to prevent the' transmission of power between said shafts, andmeans responsive'to increase in speed of the power shaft for varying said displacement element to transmit power between said shafts.

7. In combination, a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a convertible fluid pump connected with the floating member of said gearing, means responsive toi increasing speed of said power shaft for imposing an increasing load on said pump to decrease its speed and. stop the rotation thereof and for thereafter driving said pump as a motor in the opposite direction, and means for controlling the standard of operation of said speed responsive means in accordance with the pressure on said pump.

8. In combination, a variable speed power shaft, aload shaft, means for transmitting power from the power shaft to the load shaft comprising a fluid pump driven by the `power shaft .and

vconnected in fluid circuit with a fluid pump connected with the load shaft, one of said pumps being provided with means for varying the disi placement thereof, means for normally biasing said variable displacement element to a position to prevent the transmission of lpower between saidshafts, means responsive to incre-ase in speed vof the power shaft for varying said displacement element to ,transmit power between said shafts, and means responsive to pressure in said fluid circuit for opposing the shifting of saidl variable displacement element.

9. In combination, a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a fluid pump driven by said power shaft, a fluid pump driven by the floating element of the differentialgearing and connected in fluid circuit with' the first pump, one of said pumps having means for varying the displace- 75 ment thereof, means for normally biasing said displacement varying means to a position to cause both pumps to circulate fluid in the same direction in said circuit, means responsive to increase4 in speed of the power shaft to vary the displacement of said pump, and means for varying the standard of operation of said speed responsive means in accordance with pressure Var'- iations in said iiuid circuit. l

10. In combination, a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a uid pump driven by said power kshaft, a fluid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, said rst pump having means for varying the displacement thereof, means for normally biasing said displacement varying means to a position to cause the first pump to circulate fluid in the same direction in said circuit and Aat the same capacity as the second pump when .the driven shaft is stationary, and means responsive to increase in speed of the power shaft to decrease the displament of said first pump.

11. In combination, ,'a' variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a fluid pump driven by said power shaft, a fluid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, said .first pump having means for varying the displacement thereof, means for normally biasing said displacement varying'means to -a position to cause the first pump to circulate fluid in the same direction in said circuitand at the same capacity as the second pump when the driven shaft is stationary, means responsive to increase in speed crease in pressure in said fluid circuitlfor opposing the decreasein displacement of said pump.

12. In combination, .a vvariable speed power shaft, a load shaft, means for transmitting power between said shafts comprising` a fluid pump driven by the power shaft and connected in fluid circuit with a fluid motor mechanically connected with the load shaft, said fluid pump having a variable displacement, means responsive to increase` in speed of the power shaft for increasing the displacement of said pump, and means responsive to increase in pressure in said fluid circuit for opposingthe increase in displacement of said pump.-

13. In combination, an engine having a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a convertible fluid pump connected with the floating member of said gearing, and means responsive to increasing speed of said power shaft for imposing an! increasing load on said pump to decrease its t unload said pump at idling speed of said engine..

14. In combination, a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a fluid pump driven by said power shaft, a fluid pump driven by the floating element of the differential gearing and connected in uid circuit with the first pump, one of said pumps having means for varying the displacement thereof, means for normally biasing said displacement varying means to a position to cause both pumps to circulate fluid in the same direction in said circuit and at the same capacity sponsive to the speed of the power shaft to operate said displacement varying means, and control means for said speed responsive means operable in one position to increase the displacement with increasing speed and in another position to decrease the displacement with increase ir Speed. l

l15. In combination, a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a fluid pump driven by said power shaft, a fluid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, one of said pumps having means for varying the displacement thereof, means for normally biasing said displacement varying means to a position to cause both pumps to circulate fluid in the same vdirection in said circuit and at the same capacity when the driven shaft is stationary, and means responsive to increase in speed of the power shaft i of the pump to a position to prevent the trans-'- mission of power between said shafts, means responsive to increase in speed of the power shaft for varying the displacement of said pump to drive the load `shaft in one direction, and means responsive to increase in speed of the power shaft for varying the displacement of said pump in a direction to drive the load shaft in the opposite direction. g

17. In combinatiom an engine having avariable. speedpower shaft, a load shaft', means for tra'risrriitting power between said shafts comprisling a fluid pump driven by the power shaft andI connected in fluid circuit with a fluid motor mechanically connected with the load shaft, said uid pump having an element for varying the displacement thereof, means for normally biasing the variable displacement element` of the pump to a position to prevent the transmission of power between said shafts, and means responsive to increase in speed of the power shaft above when the driven shaft is stationary, means reidling speed for varying the displacement of tial gearing connecting said shafts, a fluid pump driven .by said power shaft, a fluid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, said first pump having means for varying the displacement thereof, means for normally biasing'said displacement varying means to a position to cause the first pump to circulate fluid in the same direction in saidcircuit and at the same capacity as the second pump when the driven shaft is stationary, and .means responsive to increase in speed of the power shaft above idling speed to decrease the displacement of said first pump. l

v 19. In combination, an engine having a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a reversibleV fluid pump driven by said power shaft, a convertible fluid pump driven by the floating eleopposite direction, said biasing means being crease in speed of one `of said shafts lto first de stronger than said speed responsive means at idling speed of said engine. l

20. In combination,y a variablefspeed power shaft, 'a driven shaft, differential gearing connecting said shafts, aconvertible fluid pump driven by 'said power shaft, a convertible fluid pump driven by the floating element of the differential gearing and connected in fluidicircuit with the ilrst pump, said'first pumphaving'means for varying and. reversing the displacement thereof, means for normally biasing said displacement varying means to a position to cause both pumps to circulate fluid in the same direction in` said circuit,and means responsive to increase the displacement and thenreverse the same and increase it in the opposite direction.

21. In combination, a variable speed power shaft, a driven shaft, differential gearing connecting said shaft, a convertible fluid pump driven by said power shaft, a convertible fluid pump driven by the floating element of the differential gearing andy connected in fluid circuit with the first pump, said first pump having means for varying and reversing the displacement thereof, means for normally biasing said displacement varying means to a position to cause both pumps to circulate fluid inthe same direction in said circuit, means responsive to increase in speed of one of said shafts to-rst decrease the displacement and then reverse the same and increase it in the opposite direction, and means responsive to increase in pressure in said fluid circuit for opp'osing the change in displacement of vsaid pump.

22. In combination, a differential gearing having three rotary elements, a power shaft connected to` one of said rotary elements, said differential gearing having three co-aXial shafts connected to the rotary elements thereof and extending from said gearing in axial alignment with said power shaft, the center co-axial shaft comprising a driven shaft, a pair of fluid pumps connected in fluid circuit and having rotor elements mounted co-axially with said driven shaft, one of said rotors being connected to the intermediate co-axial shaft while the other rotor is connected to the outer co-axial shaft.

23.111 combination, a drive shaft, a. rotary housing connected to said drive shaft and provided with an internal ring gear, a spider jourlng.

being mounted 'upon the sleeve extension of said sun gear, and the other rotor being mounted upon a hollow shaft surrounding said sleeve extension and connected with said ring gear hous- 24. In combination, a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a fluid pump drivenby said power shaft, a fluid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, one of said pumps having means for varying the displacement thereof above and below the displacement of the other pump, means for normally biasing said displacement varying means to a position to cause both pumps to circulate fluid-in the same direction in said circuit and atthe same capacity wl'ien the driven shaft is stationary, means responsive to increase in speed of one of said shafts to operate said displacement varying vmeans to decrease the displacement of said pump 25. In combination, a variable speed ,powerv shaft, a driven sha/ft, differential gearing connecting said shafts, a fluid pump driven by said power shaft, a fluid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, one of said pumps having means for varying -the displacement thereof above and belowl the other pump, biasing means for normally biasing said displacement means in one direction, a stop for limiting the movement of said displacement varying means by said biasing means to a position to cause both pumps to circulate fluid in the same direction in said circuit and at the same capacity when the driven shaft is stationary, said stop including a second biasing means opposing the first biasing means and being of greater strength than the first biasing means, means responsive Ato'increase in speed of one of said shafts for moving said displacement means against said first biasing means to drive the driven shaft in one direction, and means for at will movingsaid displacement means against the second biasing means vto reverse the ydirection of operation of said driven shaft.

26. In combinaiton, a fluid pump having means for varying the displacement thereof, biasing means for normally biasing said displacement varying means in onedirection, operating means for moving said displacement means in the opposite direction, a stop for limiting the movement of said biasing means to a predetermined position, said stop including a second biasing means opposing the rst biasing means and being of greater strength than the first biasing means, and operating means for moving said stop in opposition to the second biasing means.

27. In combination, a variable 4speed power shaft, a fluid pump driven by said power shaft and having means for varying the displacement thereof, biasing means for normally biasing said displacement varying means in one direction, fluid pressure operating means for moving said displacement means in the oposite direction, a stop for limiting the movement of said biasing means to a predetermined position, s'aid stop lncluding a second biasing means opposing the flrst biasing means and being of greater strength than the first biasing means, fluid pressure operating means for moving said stop in opposition to the second ,biasing means, a control pump driven by said power shaft and having a pressure variable with the speed of said shaft, and rmeans for at will connecting said control pump for operation of either of said fluid presssure operating means.

28. In. combination, a variable speed power shaft, a fluid pump driven by said power shaft and having means for varying the displacement, thereof, biasing means for normally biasing said displacement varying means in one direction, fluid pressure operating means for moving said displacement means in the opposite direction, a stop for limiting the movement of said biasing means to a predetermined position, said stop including a second biasing means opposing the first biasing means and being of a greater strength than the first biasing means, fluid pressure operating means for moving said stop in opposition to the second biasing means, a'control pump driven by said power shaft and having a pressure variable .with the speed of said shaft, means for at will connecting said control pump for operation of either of said fluid pressure operating means, and means responsive to the pressure developed by said fluid pump for decreasing the output pressure of said control pump.

29. In combination, a variable speed power shaft, a driven shaft, differential. gearing connectingsaid shafts, a convertible fluid pump driven by said power shaft, a convertible fiuid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, said first pump having means for varying and reversing the displace--l Ament thereof, a servo-motor for operating said displacement varying means and having a varfable control element, means for normally bias- Aing said variable control element t'o a'position to maintain said displacement varying means in a position to cause the rst pump to circulate iiuid in the same direction in said circuit and at the same capacity as the second pump when trol pump driven by one of said shafts for operating said fluid pressure operating means in accordance with the speed of said shaft.

30. In combination, a variable speed powerl shaft, a driven shaft, differential gearing connecting said shafts, a convertible fluid pump driven by saldrpower shaft, a convertible fluid pump driven by the floating element of the differential gearing and connected in fiuid circuit with therst pump, said first pump having means/for varying and reversing the displacement thereof, a servo-motor having a power piston for operatingsaid displacement varying means, a valve element carried by and cooperating with said piston to control the movement thereof, means for normally biasing said valve element to a position to maintain said displacement varying means in a position to cause the first pump to circulate fluid in the same direction in said circuit and at the same capacity as the second pump when the driven shaft is stationary, a control piston for operating said valve element from its biased position to first decrease the displacement and then reverse the same and increase it in the opposite direction, and a control pump driven by the power shaft and sup'- plying operating uid to said control piston at a pressure variable in accordance with the speed of said power shaft.

31. In combination, a variable speed power shaft, a driven shaft, differential gearing connectingr said shafts, a convertible fluid pumpl driven by said power shaft, a convertible iiuid pump driven by the floating element of the dif-A ferential gearing and connected in fluid circuit with the first pump, said first pump having means for varying and reversing the displacement thereof, a servo-motor having a power piston for operating said displacement varying means, a valve element carried by and cooperating with said piston to control the movement thereof, biasing means for normally biasing said valve element in one direction, a stop for limiting the movement of said valve element to a position to cause the first pump toycirculate iiuid in the vsame direction in said circuit and at the same capacity as the second pump when the driven shaft is stationary, a control piston for operating said valve element from its biased position to first decrease the displacement and then reverse the same and increase it in the opposite direction, said stop being l carried by a second control piston having .biasing means for maintaining said stop in its normal position against said ,first biasing means, a`

control pump driven by the power shaft and supplying operating fluid at ay pressure variable i-n accordance with the speed of said power shaft, and a control valve for connecting said control pump to operate either of said control pistons.

32. In combination, an engine having a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a convertible fluid pump driven by said power shaft, a convertible fluid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, said first pump having means for varying and reversing the displacement thereof, means for normally biasing said displacement varying means -to a position to cause the first pump to circulate fluid in the same direction in said circuit and at the same capacity as the second pump when the driven shaft is stationary, means responsive to increase in speed of the power shaft above idling speed to first decrease the displacement and then reverse the same and increase it in the opposite direction, said biasing means being stronger than said speed responsive means at idling speed vof said engine, and means responsive to the pressure in said fluid circuit for opposing the change in displacement of said first pump.

33. In combination, an engine having a variable speed power shaft, a driven shaft, differential gearing connecting said shafts, a convertible fluid pump driven by said power shaft, a convertible fluid pump driven by the floating element of the differential gearing and connected in fluid circuit with the first pump, said first pump having means for varying and reversing the displacement thereof, means for normally biasing said displacement varying means to a positiorrto cause the first pump to circulate fluid iii/the same direction in said circuit and at thy'same capacity as the second pump when the driven shaft is stationary, means responsive toincrease in lspeed of the power shaft above idling speed to first decrease the displacement and then reverse the same 'and increase it in the opposite direction, said biasing means being stronger than said speed responsive means at idling speed of said engine, means responsive to the pressure in said fluid circuit for opposing the change in dis- 15 placement of said first pump, and means for at will operating said displacement varying means to 'increase the displacement 0f the first pump above its biased value to operate the driven shaft of said displacement varying means by said biasing means to a position to cause both pumps to circulate uid in the same direction in said circuit and at the same capacity when the driven shaft is stationary, said stop including a second biasing means opposing the iirst biasing means and being of greater strength than the first biasing means, means for moving said displacement means against said rst biasing means to drive the driven shaft in one direction, and means for at will moving .said displacement means against the second biasing means to reverse the direction of operation of said driven shaft.

oLoF LJUNGs'rRoM. 

